#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
#define rep(i, a, b) for (int i = (a); i <= (b); i++)
#define per(i, a, b) for (int i = (a); i >= (b); i--)
#define endl '\n'
const int N = 2e5 + 5;

int n, m;
string s;

int main() {
  ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  cin >> s;
  n = s.size();
  int ans = 0;
  rep(i, 0, n - 1) {
    if (s[i] != 'A') continue;
    rep(j, i + 1, n - 1) {
      if (s[j] != 'B') continue;
      int k = j * 2 - i;
      if (k < n && s[k] == 'C') ans++;
    }
  }
  cout << ans;
  return 0;
}